Reactor for nitration of hydrocarbons in the gaseous phase under pressure

ABSTRACT

A reactor for nitration of saturated hydrocarbons having less than five  con atoms, alone or in admixture, in the gaseous phase under pressure is made up of a reaction enclosure, in which a tube or pipe bank is in contact with a heated fluid of high heat-exchange capacity. The inside perimeter of the tubes does not exceed 800 mm, and if circular not in excess of 250 mm, and the ratio of the surface of the tube bank, in contact with the reaction medium, to the volume of the reaction enclosure is 1:1 to 3:1. 
     The reactor apparatus further includes a mechanical means to uniformly distribute the delivery of reaction medium gases to the various tubes of the bank so that the load difference between the most loaded tube and that of the least loaded tube is equal to 10% at the most. 
     The reactor also includes a tube bank injector which feeds the tube bank to assure homogeneous mixing of all the reaction fluids in the tube bank.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 131,004 filedMar. 17, 1980, now abandoned.

FIELD OF THE INVENTION

This invention relates to a reactor for nitration of hydrocarbons in thegaseous phase under pressure.

BACKGROUND OF THE INVENTION

Various processes for the nitration of hydrocarbons have already beenproposed. Of particular interest are processes for the nitration ofpropane, ethane and mixtures of these hydrocarbons. LHonore et al., U.S.Pat. No. 3,780,115, describes nitration of propane with nitrogenperoxide in the presence of oxygen, introduced in the form of air, undera pressure of 8 to 14 bars and at introduction temperatures of thereactants in the reaction zone on the order of 200° to 240° C.

Copending application Ser. No. 25,594, of Mar. 30, 1979, now U.S. Pat.No. 4,260,838 relates to nitration of a mixture containing a substantialamount of propane. The reaction temperature and pressure, contact timeand quantitative ratios among the nitrating agent, the mixture to benitrated and the oxygenated gas are selected so that the nitrationreaction is performed in the homogeneous gaseous phase. The mixture tobe nitrated contains propane and one or more other alkanes having up tofive carbon atoms in the molecule.

The conditions for nitration of ethane are the object of copending Ser.No. 94,153 of Nov. 14, 1979 now U.S. Pat. No. 4,313,010. According tothis process the quantitative ratios of the various constituents of thereaction mixture, the reaction contact time and the reactiontemperatures and pressures are selected and controlled so that nitrationof the ethane takes place in a homogeneous gaseous phase, and as afunction of the range of nitroparaffins expected to be obtained.

As in the previous processes for nitrating propane or propane basemixtures, the nitration reaction can be performed in the presence of anactive agent carrying an easily transferable NO or NO₂ group, such as2-nitropropane or nitroethane, alone or in mixture, possibly recycledreaction product. These nitrations are also advantageously performed inthe presence of a gas, inert in the reaction (hereinafter an "inertgas"), selected from nitrogen, carbon monoxide, carbon dioxide,hydrogen, methane, argon or a mixture of any of these gases.

For all these processes, the highest yields are obtained only by workingwith a gradual and regular heat regime, i.e. by controlling thetemperature curve inside the reaction zone; this curve must be smooth,i.e. have a regular growth without inflection points. Such a heat regimecan be obtained only by avoiding any racing of the reaction and theappearance of high temperatures at certan points of the reaction zone.

OBJECTS AND SUMMARY OF THE INVENTION

There has now been found a type of reactor that can be used in allnitrations of saturated hydrocarbons having less than five carbon atoms,in the gaseous phase under pressure. This reactor by its structure makesit possible to obtain a heat regime with regular progression during thenitration reaction, i.e. the evolution of the reaction temperature curveis continuous and progressive, without sudden acceleration of thereaction rate and without appearance of temperature peaks at variousspots of the reaction zone.

It is therefore an object of the invention to construct the reactor of ametal which will resist corrosion by contact with a nitrating agent. Itis also an object of the invention to provide a reactor having efficientheat exchange characteristics and possessing a good response to thetemperature elevation curve during the reaction.

It is a further object of the invention to provide a reactor wherein thedifference in temperature between the hottest point on the tube or pipebank of the reactor does not exceed about 20° C.

It is another object of the invention to construct the reactor of ametal which can resist rupture due to pressures in the tubes or pipes,which carry the heating fluids, that can reach 100 bars at the ambientoperating temperatures of the nitration reaction.

It is a further object to construct the reactor and themixture-distributor unit of a metal that will permit higher yields ofthe nitration reactions while concurrent oxidation reactions are kept toa minimum.

It is a still further object to provide a reactor consisting of pipes inwhich the reaction mixture is very evenly distributed and homogeneouslymixed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a vertical section of the prototype reactor of Example 1,infra.

FIG. 2 is a cross-section taken at 2--2 in FIG. 1 showing thedistribution of the 37 pipes of the reactor embodiment.

FIG. 3 is a section of the lower part of the pipe bank.

FIG. 4 is a cross-section taken at 4--4 in FIG. 3 of the pipe bankshowing the distribution of the reaction mixture in the pipes.

FIG. 5 is a cross-section taken at 5--5 in FIG. 3 showing thedistribution of the reaction mixture.

FIG. 6 is a graph showing the temperature variation in the reactor tubesfor the reaction conditions described in Example 1, infra.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The reactor, according to the invention, is made up of a reactionenclosure, in which a tube or pipe bank is in contact with aheat-carrying fluid, with a high heat exchange capacity. Theheat-carrying fluid which carries the heat of the nitration reaction orthat necessary for heating the reactants can be vapor, e.g. steam, abath of molten salts or any suitable heat-carrying fluid. Theheat-carrying fluid is selected so that the temperature of the outsideskin of the tubes is kept constant with only about 20° C. differencebetween the hottest point and the coldest point of the tubes.

Most often, the tube bank is immersed in the heat carrying fluid and thenitration reaction takes place inside the tubes. But it is possible,within the scope of the invention, to envisage nitration taking placeoutside the tubes, the heat-carrying fluid being housed inside thetubes.

The size of the tubes of the bank plays a role in the regular increaseof the temperature during the progress of the reaction. The shape of thecross section of the tubes makes no difference if it allows a good flowof the gaseous fluids, either circular or oval, provided the insideperimeter of the tubes of the bank is at most equal to 800 millimeters;the inside diameter of the tubes of circular section is at most equal to250 millimeters.

Further, it has been noted that the judicious choice of the ratiobetween the surface of the tube bank, in contact with the reactionmedium, and the volume of the reaction enclosure has a favorableinfluence on the smooth and regular increase of the temperature duringthe reaction. A ratio range giving this favorable result is 0.1 to 20.1,preferably 0.5 to 5:1, and in particular 1 to 3:1.

Obtaining nitration products with good yields is also related to theregular maintenance of contact times in all the tubes of the bank;moreover, this is valid only with comparable deliveries (throughputs) inthe various tubes of the bank. The regular distribution of the deliveryin the various tubes of the bank can be assured by a mechanical meanswith which the reactor is equipped. It is advantageous to distribute thedelivery so that the maximal load difference between the most loadedtube and the least loaded tube does not exceed 10%.

The reaction is fed by the action of an injector which assures ahomogeneous mixing of all the reaction fluids.

The tube bank is made of a metal which resists corrosion by chemicalaction with the nitrating agent: nitric acid, nitrogen peroxide, aloneor in mixture, or any other agent carrying an easily transferable NO orNO₂ group; and the metallic coupling formed with the metal of theinjector is critically selected so that it does not cause ignition ofthe reaction fluids at the input of the reaction chamber.

The nitration reactor described above provides excellent performance inall types of nitrations of hydrocarbons in the gaseous phase underpressure, particularly saturated hydrocarbons of less than five carbons,in particular ethane and propane and their mixtures, possible in thepresence of oxygen, recycling products, adjuvants and inert gases. Theprocesses described in the disclosures, cited above, are advantageouslyused in the present reaction.

The reactor, made up of a bank of pipes, has from the structuralviewpoint three types of characteristics.

The first characteristic deals with the section and shape of the pipes;the ratio between the inside surface of the pipes and the inside volumeof the bank is an important factor to obtain a good flow of the reactiongases and good heat exchange. This ratio is S/V and defines thethickness of the gas stream.

The second characteristic relates to the irregular arrangement of thebaffles on the inside of the pipe bank, of the segmented (according tothe figures) disk or ring type. The distance between the two baffles isminimal in the reaction zone. This arrangement is intended to assure thebest heat exchanges between the heat-carrying fluid and the reactiongases. This arrangement is intended to reduce as much as possible sitesof low heat transfer in the zone where the reaction occurs and in thezone where the effluents are cooled.

According to the third characteristic, the reactor is equipped with areaction gas mixer combining the technology of dynamic and staticmixing. The distributor unit, all or part of its surface being incontact with the heat-carrying fluid, has the role of distributing thegases in the various pipes and is characterized by a succession ofwidenings and narrowings of the sections for passage of the reactiongases, in particular a considerable narrowing (calibrated orifice) ofthe passage section at right angles with each pipe of the bank (at thebase of each pipe in the axis of the pipe, see FIG. 3). This restrictionof the gas passage makes possible a better distribution of the gasesbetween each pipe so that the load difference between the most loadedtube and that of the least loaded tube is equal to 10% at the most. Onthe other hand, the reactor is performing only to the extent that theheat exchanges are efficient and is characterized by parameters thatdefine the features of the process, namely, the values of the ratiosQ/US and Q'/US.

Q designates the heat released by the reaction, Q' designates the totalheat exchanged with the heat-carrying fluid, i.e. the sum of the totalheat given up to the mixture of reaction gases and the heat given up tothe heat carrier salt during the reaction and cooling of the gases. Udesignates the over-all heat exchange coefficient and S the availableexchange surface.

The choice of the ratios Q/US and Q'/US can be selected based on processfeatures which characterize the mode of circulation of the heat-carryingfluid to the outside of the pipe bank.

The quality of the nitration reaction performed from a mixture ofsuitable composition (hydrocarbon, oxygen nitrating agent and possiblyinert gases, and organic compounds such as recycled nitroparaffins)depends on: the quality of the heat exchanges of the reactor; thehomogeneity of the reaction mixture and the uniformity of itsdistribution in the various pipes of the reactor bank, and the nature ofthe metal which constitutes the reactor bank and the mixer-distributorunit.

In the reactor for nitration of hydrocarbons in the gaseous phase underpressure, made up of a reaction enclosure in which a platelike or pipebank is in contact with a heat-carrying fluid with great heat exchangecapacity, the heat exchanges are assured by a cocurrent orcountercurrent circulation, preferable cocurrent, of a heat-carryingfluid able to function satisfactorily at nitration temperatures, forexample, between 200° and 450° C. Circulation of the heat-carrying fluidis performed to assure both a sufficient heat exchange at the zone wherethe reaction is maximal and preheating of reagents to reaction startingtemperature, gradual enough to avoid too quick a reaction.

The heat-carrying fluid and its mode of circulation on the outside ofthe bank are selected so that temperatures of the outside skin of thepipes between the coldest point and the hottest point are kept constantat no more than 25° C. difference.

The size of the pipes of the bank plays an important role in regard tothe regular increase of the temperature of the gases during thereaction. A suitable choice of these dimensions makes it possible tocontrol the temperature profile inside the pipes both in the preheatingzone and in the reaction zone and in the part corresponding to coolingof the reaction products. In particular, a gradual increase of thetemperature in the preheating zone assures stable thermal operatingconditions and avoids racing of the reaction which would be reflected bytoo high a maximum temperature for a correct nitration.

The judicious choice of the ratio between the surface of the pipe bankin contact with the reaction medium and the volume of the reactionenclosure, S/V, has a favorable influence on the regular increase of thetemperature during the reaction, when this ratio is between 22 and 425m⁻¹, preferably 50 and 250 m⁻¹ and in particular 120 and 250 m⁻¹.

The shape and cross section of the pipes (circular, oval or platelike)does not matter as long as it allows a good flow of the gaseous fluidand the heat-carrying fluid assuring the requisite transfer. For this,the inside perimeter of the pipes of the bank should be less than 800millimeters, preferably less than 500 millimeters, while the thicknessof the gas stream should not exceed 150 millimeters, preferable 50millimeters.

The length of the pipes should be sufficient so that, when the reactionis occuring, the temperature of the gaseous mixture is brought to avalue close to the temperature of the heat-carrying fluid, made up forexample of molten salts. The minimal length depends on the inputtemperature in the pipes; if it is slight, the part of the pipesallocated to preheating of the reagents to the temperature when thereaction begins is longer; therefore the total length necessary isgreater. Lengths between 8 and 12 meters are perfectly suitable.

The values of the ratios Q/US and Q'/US should be suitably selected sothat the reaction can occur under good conditions. Q designates the heatreleased by the reaction, considering that the latter begins, forexample, from 260° C.; Q'designates the total heat exchanged with theheat-carrying fluid, i.e. the sum of the heat given up to the mixture ofreaction gases to bring their temperature to 260° C. and the heat givenup to the heat-carrying fluid during the reaction and cooling of thegases. U designates the over-all coefficient of the theoretical thermalexchange calculated for reaction gases at the temperature of theheat-carrying fluid and relating to the external surface of thereactional enclosure and S designates the internal exchange surfaceavailable in relation to a pipe 12 meters long. These ratios Q/SU andQ'/SU are measured in temperature units and are valid regardless of thesize of the pipes. The ratios Q/SU are between 20° and 120° C. andpreferably between 40° and 90° C., while the ratios Q'/SU are between25° and 160° C., preferably 50° and 130° C., and make possible theperformance of a nitration reaction under excellent conditions. Theover-all exchange coefficient U can advantageously be between 20 and 300Kcal/hm² ° C. and preferably between 30 and 200.

The best heat exchanges are obtained, on the one hand, from the choiceof a suitable heat-carrying fluid, selected from mixtures of moltensalts such as nitrites and nitrates of alkali metals; and, on the otherhand, from an effective circulation of the heat-carrying fluid,characterized by a maximal reduction of the zones of least heat transferquality. An excellent heat transfer is obtained by a crosswisecirculation of the heat-carrying fluid in relation to the bank.

The tubular or platelike bank is equipped with segmented, disk or ringtype baffles, distributed irregularly along the entire axis of the bank;the distances separating two baffles being minimal at right angles withthe zone where the nitration reaction occurs.

Further, distribution of the reaction gases at the input of the pipebank, the design of the latter and the circulation of the heat-carryingfluid are such that preferably the reaction will have the greatestpossible symmetry around an axis parallel to the pipes. The bank does ordoes not comprise pipes in the central part.

The reactor is fed by a mixer-distributor unit intended, on the onehand, to assure a homogeneous mixing of the group of reagents and, onthe other hand, to distribute this homogeous mixture in a regular mannerbetween the various pipes.

The mixture assures a homogeneous mixture of the reaction fluids so thatthe maximum divergence of concentration at any point of the distributordoes not exceed 3%, preferably 1%.

Obtaining nitration products with good yields also depends on regularmaintenance of deliveries, therefore on the dwell time in the variouspipes of the bank, these latter having to be charged as identically aspossible. The mixer-distributor is equipped, for this purpose, with asuitable static device, which regularly distributes the infeed to thepipes of the bank so that the maximal load difference between theheaviest loaded pipe and the least loaded does not exceed 3%.

The mixer-distributor can be designed with or without circulation of theheat-carrying fluid over all or part of the mixing and distributionzones, the heat-carrying fluid never having to be in direct contact withthe gases.

Mixing and distribution should occur in a sufficiently short time, atmost 0.5 second, and preferably less than 0.1 second. The velocities ofthe gases in the mixer-distributor apparatus advantageously remainbetween 3 and 50 meters per second.

The mixer-distributor for the various pipes of the bank, combining thetechnology of dynamic and static mixing, is provided with a successionof widenings and narrowings of gas passage sections, in particular aconsiderable narrowing of the passage section at right angles with eachpipe of the bank; this restriction makes possible a better distributionof the gases between each pipe.

The pipe bank and the mixer-distributor unit should be made of metalsable to resist corrosions caused by nitrating agent and resistant to theheat-carrying fluid. This metal should further be selected so that itdoes not have the effect of favoring oxidation reactions that competewith the nitration. In particular, certain austenitic stainless steelswith nickel-chromium give total satisfaction. They are of the Z 12 CNS25-20, Z 3 CN 18-10, A 310 A, A 1S1 310S types and the Inconels, Inconel600, norm AFNOR ZNCSE 72-14 or ZNC Fe 72-14 (AFNOR standard).

Composition of said steels:

    ______________________________________                                        Z3 C N 18-10:    C max. 0.035;                                                                              Cr 18.5; Ni 10.5                                Z 12 CNS 25-20                                                                                 C max. 0.10; Cr 25; Ni 20                                    AISI 310 S.                                                                   Inconel 60:      C max. 0.2;  Cr 14-17; Ni ≦ 72;                                        Fe 6-10;     Cu < 0.7; Si < 0.5;                                              Mn<1.                                                        ______________________________________                                    

The reactor of the invention is characterized by the structuralarrangements that will be cited below and the parameters relating to thetemperature of the pipe skin, to the diameter of the pipes, to theratios S/V, Q/S, QUS and U, which are set forth below.

In FIG. 1, the reaction mixture is introduced through the lower part ofvertical pipe bank (1) and vertical lines (2) represent some pipes inwhich the reaction mixture circulates upwardly.

The heat-carrying fluid circulates outside the pipes (2) in the samedirection, cocurrent with the gases. The heat-carrying fluid isintroduced and removed through inlet and outlet pipes (3) and (4).Circulation of the heat-carrying fluid is controlled by the arrangementof baffles which extend partly across the reactor, hereinafter segmentedtype baffles (5), distributed irregularly and with minimal distancetherebetween at right angles to the length of the reactor, i.e. in thecentral part of the pipe between B and B'. (The intervals in dottedlines C and C' correspond to the parts of the pipe (not shown) in theheight of 12 meters).

FIG. 2 corresponds to a cross section with distribution of 37 pipes (2)at 2--2 of FIG. 1. Segmented baffles 5₁ and 5₂ can be seen in thisfigure.

FIGS. 3, 4 and 5 each show distribution of the gases in the reactorsystem.

The reaction gas mixer is not shown in FIG. 3. At the output of themixer, the gases arrive by conduit (1) at the base of thedivider-distributor device that causes accelerations and decelerationsin the distribution zone at (6) (FIGS. 3 and 5). The gases enter adeceleration zone from which radiate conduits (7) in which the velocityof the gases is accelerated. At this level, the gases distributed byconduits 7 are distributed as shown in FIG. 4 along section 4--4 byradial distribution channels 8 and three circular distribution channels8₁, 8₂, 8₃ ; in this zone, there is deceleration. The distributionchannels are at the base of the pipes and lie in their axes. Then thegases leaving the channels are forced toward a calibrated passage 9 atthe input and in the axis of the pipes, which involves a finalacceleration of the gases at the input of the pipes. A tube bankinjector is utilized to assure homogeneous mixing of all reactionfluids.

EXAMPLE I

A prototype reactor for the nitration of hydrocarbons in the gaseousphase under pressure is made up of a bank of 37 pipes.

The pipe bank is made up of 37 stainless steel pipes of Z 12 CNS 25-20(CO 10, Cr 25, Ni 20) 12 meters long, with an inside and outsidediameter of 21.7 and 26.9 millimeters distributed at a triangular pitchof 46 millimeters. It is possible to block a certain number of the pipesto use n pipes of the bank, n being selected to be about 30, dependingon the desired operating conditions.

The ratio between the inside surface of the pipes and the inside volumeof the bank is 184 m⁻¹.

Heat exchanges are assured by a circulation cocurrent with theheat-carrying fluid made up of a mixture of molten salts: 40% sodiumnitrite (NaNO₂), 7% sodium nitrate (NaNO₃) and 53% potassium nitrate(KNO₃).

Segmented baffles are arranged irregularly inside the pipes to allow avariation of a ratio of 1 to 3 of the heat-carrying fluid.

The ratios Q/SU and Q'/SU can vary form 55 to 80 for Q/SU and 70-105 forQ'/SU while the ratio between the heat to be evacuated can vary between3000 and 6000 Kcal/hm².

The reaction gases are mixed in a double pipe mixer provided withhelicoidal wings assuring a homogeneous mixing of such quality that themaximal variation of concentration at any point of the distributor doesnot exceed 3%, in a period of 0.03 to 0.04 seconds for velocities of 4to 25 meters per second.

The mixture of reaction gases then circulate in a distributor-dividerwhere it is subjected to a succession of decelerations and accelerationsduring which the velocities are kept in an interval of 2 to 25 metersper second. Intake of the reaction mixture in each pipe of the bankoccurs through a calibrated orifice that causes a considerable load lossand gas velocities increasing from 15 to 30 meters/second, which makespossible a good distribution of the gas mixture between the variouspipes of the bank: the maximal divergence between the deliveries at theinput of each pipe does not exceed 3%.

By a device with stationary thermocouples and one with a mobilethermocouple, the thermal profile of the temperatures of the reactionenclosure is known; this knowledge makes it possible to vary theparameters of the reaction such as Q/SU, U, contact time, delivery ofthe heat-carrying fluid, while controlling the evolution of thenitration.

1a. Nitration in a reactor having 36 pipes in operation

Temperatures of the molten salts

=input: 299° C.

=output: 300° C.

Pressure of the gases in the mixer-distributor: 8.8 Kg/cm² effective

                  TABLE I                                                         ______________________________________                                                       REACTOR    REACTOR                                                            INPUT      OUTPUT                                                             kg/h       kg/h                                                ______________________________________                                        C.sub.3 H.sub.8  380.78       335.79                                          C.sub.2 H.sub.6  1.74         1.73                                            C.sub.4 H.sub.10 3.76         2.76                                            NO.sub.2         102.08                                                       O.sub.2          20.64                                                        N.sub.2          71.16        72.                                             CO                            9.24                                            CO.sub.2                      15.41                                           NO                            38.78                                           H.sub.2 O                     32.05                                           methanol CH.sub.3 OH          0.05                                            acetaldehyde CH.sub.3 CHO     2.97                                            ethanol C.sub.2 H.sub.5 OH    --                                              acetonitrile CH.sub.3 CN      1.86                                            acetone (CH.sub.3).sub.2 CO   4.24                                            propionitrile C.sub.2 H.sub.5 CN                                                                            .56                                             nitromethane CH.sub.3 NO.sub.2                                                                              21.43                                           Nitroethane C.sub.2 H.sub.5 NO.sub.2                                                                        5.32                                            2 Nitro-propane(CH.sub.3)CHNO.sub.2                                                                         25.12                                           1 Nitro-propane C.sub.3 H.sub.7 NO.sub.2                                                                    10.57                                           Nitrous acid HNO.sub.2        .98                                             Nitric acid HNO.sub.3         .51                                             ______________________________________                                    

Dwell time calculated as follows: 8.5 seconds dwell time for a constantgas delivery equal to voluminal delivery at the input of the pipes,under a constant pressure equal to the input pressure and a constanttemperature equal to the average temperature of the heat-carrying fluid.

    ______________________________________                                        Q = heat released during reaction                                                                  120 172 Kcal/h                                           (going from 260° C.)                                                   heat supplied to reagents to bring them                                                            31 972 Kcal/h                                            to 260° C.                                                             Q' = total heat exchange between the                                                               152 144 Kcal/h                                           gases and the heat-carrying fluid                                             Q/S = 4005 Kcal/hm.sup.2                                                                           Q'/S = 5,166 Kcal/hm.sup.2                               Q/US = 63° C.                                                          U = 64.6 Kcal/hm.sup.2 °C.                                                                  Q'/US = 80° C.                                    ______________________________________                                    

The profile of the temperature in the reactor pipes appears on the curveof FIG. 6, the distance traveled in the tube by the reaction mixtureexpressed in meters is on the x-axis and the temperatures in ° C. on they-axis.

1b. Nitration in a 36-pipe reactor

Temperature of molten salts

=input: 329° C.

=output: 331° C.

Pressure input pipes: 9.7 kg/cm² effective

                  TABLE II                                                        ______________________________________                                                 INPUT KG/H                                                                              OUTPUT KG/H                                                ______________________________________                                        C.sub.3 H.sub.8                                                                          417.21      377.67                                                 C.sub.2 H.sub.6                                                                          1.43        1.42                                                   C.sub.4 H.sub.10                                                                         4.49        2.56                                                   NO.sub.2   121.99                                                             O.sub.2    28.98                                                              N.sub.2    96.88       95.47                                                  CO                     8.92                                                   CO.sub.2   .51         17.35                                                  NO                     68.32                                                  H.sub.2 O              42.68                                                  CH.sub.3 OH            .51                                                    CH.sub.3 CHO           11.65                                                  C.sub.2 H.sub.5 OH     --                                                     CH.sub.3 CN            .03                                                    (CH.sub.3).sub.2 CO    3.10                                                   C.sub.2 H.sub.5 CN     --                                                     CH.sub.3 NO.sub.2                                                                        .11         18.84                                                  C.sub.2 H.sub.5 NO.sub.2                                                                 7.92        11.92                                                  (CH.sub.3).sub.2 CHNO.sub.2                                                              46.82       55.80                                                  C.sub.3 H.sub.7 NO.sub.2                                                                 3.56        13.04                                                  HNO.sub.2              .42                                                    HNO.sub.3              2.96                                                   ______________________________________                                    

Dwell time according to definition example I=6.5 seconds

    ______________________________________                                        Q = 132 850 Kcal/h                                                            Q' = 174 850 Kcal/h                                                           Q/US = 49° C.                                                                            Q'/US = 47.5° C.                                     Q/S = 4514 Kcal/hm.sup.2                                                                        Q'/S = 5940 Kcal/hm.sup.2                                   U = 92 Kcal/hm.sup.2 °C.                                               ______________________________________                                    

EXAMPLE II

An industrial reactor for the nitration of hydrocarbons in the gaseousphase under pressure is made up of a bank of 1156 pipes and functionsunder the same principles, which define a gas distribution system.

The pipe bank of this reactor is made up of 1156 pipes of stainlesssteel of the type Z 12 CNS 25-20(CO 10,Cr, 25,Ni 20, silicon≦1) or AlSi310, with inside and outside diameters of 22.10 and 25.4 millimeters,and 12 meters long. The ratio between the inside surface of the pipes ofthe bank and the inside volume of the bank is 181 m⁻¹.

For nitration of an ethane-propane mixture, the ratios Q/SU and Q'/SUcan vary between 45 and 60° C. for Q/SU and between 55° and 80° C. forQ'/SU.

As in the preceding reactor the heat exchanges are assured by acocurrent circulation of a mixture of molten salts with 40% by mass ofNaNO₂, 7% NaNO₃ and 53% KNO₃.

The pipe bank exhibits a symmetry of revolution in relation to an axisparallel to the pipes, the baffles placed on the inside of the pipe bankare of the disk type and rings are distributed irregularly along theaxis of the bank, the distances separating two baffles being minimal atright angles with the zone where the reaction occurs.

The mixture of reaction gases, the distribution-division of the mixture,its intake, the thermal control of the temperatures of the reactionenclosure are achieved under the same conditions as in Example 1.

This type of reactor is suited to an industrial scale of nitration ofany hydrocarbon or mixture of saturated hydrocarbons lower than C₅, andfor example nitration of a mixture of ethane and propane, according tothe following balance.

Input pressure=11 effective bars

Temperature of the molten salts: 330° C.

Input temperature of the gases: 150° C./output temperature: 340° C.

                  TABLE III                                                       ______________________________________                                                              OUTPUT PIPES                                                     INPUT PIPES KG/H                                                                           KG/H                                                    ______________________________________                                        C.sub.2 H.sub.6                                                                          6554.79        6176.43                                             C.sub.3 H.sub.8                                                                          6569.38        5733.33                                             C.sub.4 H.sub.10                                                                         1.06           .96                                                 iso C.sub.4 H.sub.10                                                                     5.01           4.00                                                CO         1813.41        2176.13                                             CO.sub.2   3864.15        4672.09                                             N.sub.2    41.35          41.35                                               O.sub.2    734.44                                                             NO         38.66          1985.47                                             NO.sub.2   3958.94                                                            N.sub.2 O.sub.4                                                               N.sub.2 O  67.86          67.86                                               H.sub.2 O  72.35          991.36                                              Nitromethane                                                                             .24            585.71                                              Nitroethane                                                                              55.77          475.16                                              1 Nitro-Propane                                                                          149.98         352.07                                              2 Nitro-Propane                                                                          874.79         929.95                                              2 Nitro-Butane                                                                           .08            1.14                                                Methanol                  52.12                                               Ethanol                   15.20                                               Formaldehyde              12.31                                               Acetaldehyde              242.06                                              Acetone                   106.38                                              Formic acid               .46                                                 Acetic acid               6.08                                                Acetonitrile              30.39                                               Propionitrile             1.98                                                CHNO.sub.2                29.33                                               HNO.sub.3                 106.37                                              ______________________________________                                    

From the foregoing it will be evident that an improved nitratingreactor, having the advantages described above, has been designed andconstructed.

It will be obvious to those skilled in the art, that various changes maybe made without departing from the scope of the invention, and theinvention is not to be considered limited to what is specificallydescribed in the specification.

What is claimed is:
 1. In a reactor for nitration in the gaseous phaseunder pressure of the type including a reaction enclosure having upperand lower ends, a conduit for introducing reaction gases into saidenclosure, means for introducing heat-carrying fluids, means forextracting the heat-carrying fluids, and a bank of tubes containedwithin the enclosure, the improvement comprising;means for distributingthe introduced reaction gases to said tubes, said distributing meansbeing disposed between said conduit and said tubes and defining meansfor successively decelerating and accelerating said introduced gases,said successively decelerating and accelerating means including firstchannel means disposed at the base of said tubes, said first channelmeans comprising a plurality of concentric circular decelerationchannels disposed substantially normal to said tubes, and accelerationpassages connected between said deceleration channels and said tubes,and second channel means extending from said conduit through adeceleration chamber to acceleration channels radiating at an angle awayfrom said deceleration chamber toward, and interconnecting, said firstchannel means, each of first channel means and said second channel meanssuccessively decelerating and accelerating said gases, whereby uponpassing through said first and second channel means from said conduit,said gases become homogenously mixed prior to being distributed to saidtubes.
 2. The improvement of claim 1 wherein:said acceleration passagesare calibrated, and said second channel means comprises a decelerationchannel connecting said conduit with said deceleration chamber, andhaving a larger cross-sectional area at the one end joining saiddeceleration chamber than at the other end joining said conduit.
 3. Theimprovement of claim 1 whereinsaid deceleration channels areinterconnected by a plurality of radially extending interconnectingchannels the latter being substantially normal to said decelerationchannels and said tubes.
 4. A reactor for nitration in the gaseous phaseunder pressure comprising a reaction enclosure having an upper end and alower end and containing a vertical plate bank of tubes, a conduit forthe introduction of reaction gases at the lower end of the reactionenclosure, means for introducing and extracting heat-carrying fluids,wherein the plate bank of tubes is equipped with segmented compartmentsseparated by disc or ring-type partitions irregularly distributed alongthe length of the bank; the distances separating two partitions bengminimal in the central portion of the bank in a region defining areaction zone, whereinthe reactor includes at said lower end means fordistributing said reaction gases to different tubes of the bank, saiddistributing means being disposed between said conduit and said tubesand defining means for successively decelerating and accelerating theintroduced gases, said successively decelerating and accelerating meansincluding first channel means disposed at the base of said tubes, saidfirst channel means comprising a plurality of concentric circulardeceleration channels disposed substantially normal to said tubes, andacceleration passages connected between said deceleration channels andsaid tubes, and second channel means extending from said conduit througha deceleration chamber to acceleration channels radiating at an angleaway from said deceleration chamber toward, and interconnecting, saidfirst channel means, each of said first channel means and said secondchannel means successively decelerating and accelerating said gases,whereby upon passing through said first and second channel means fromsaid conduit, said gases become homogenously mixed prior to beingdistributed to said tubes.